Power system restoration becomes more important daily due to the upcoming significant amount of uncertainties and risks from integrated variable renewable energy resources, market activities and stressed power system facilities. Restoration planning is an off-line process ensuring an effective coordinated restoration following a wide-area blackout based on the best knowledge available. Due to the size and complexity of the problem, conventional planning technologies have to rely on a number of manual studies based on certain selected load scenarios, size-reduced network models and fixed generation profiles, which may not be adequate for the future smart-grid with frequent system reconfigurations, variable energy resources and responsive loads.
Planning is an integrated part of power system operation. It includes a number of offline analyses and simulations completed prior to real-time. Planning is essential to the real time operation, as the outcomes of planning not only can be used to improve the understanding about the grid status and potential problems at various time horizons in the future, some are even directly used by the operator for making real-time decisions. Planning presumably is to generate the best estimation of the future status of the grid based on the most updated information and the best technology available.
Power system restoration planning is an important undertaking, specifically aimed at helping the grid operator to be better prepared after a large-scale blackout. Because of the complexity of the power system and lack of precise information about grid status during the restoration process, although not all the restoration issues can be addressed ahead of time, planning still provides crucial support such as formulation of appropriate strategies, identification of potential transient and steady-state reliability problems along the way, assessment of the status or readiness of key restoration components, and essential trainings.
The complexity and dimensionality of the problem, incompleteness of information, and tight runtime constraints make the power system restoration one of the most challenging problems in engineering disciplinary. First, it can be seen as an optimization problem concerning resource selection, path finding, and load pickup. Furthermore, the stability of electrical power system is determined by physics and rendered as different transient and steady-state complex problems. Thus, the solutions to these problems depend on distinctively different mathematical models and methods under different assumptions. Moreover, these problems, most likely presented in large-scale and partial information, must be solved under tight runtime constraints to be practical.
Planning for power system restoration following a complete or wide-area blackout is presently more important than ever before. In the past, restoration planning wasn't a central issue to power companies as blackouts were considered very rare events. Most power companies would only conduct restoration planning a few times per year, and many plans used for guiding the restoration are currently outdated or not comprehensive. Due to the rapid growth of variable generation resources, increasing involvement of responsive loads, development of less-dispatchable distributed generation resources and more stressed grid infrastructures, the system operators are seeing ever changing problems and an urgent need to manage the increasing risk of large-scale blackouts.
Comprehensive restoration planning could be one of the most challenging issue to engineering science as it not only includes almost all difficult issues encountered in normal operation condition, many additional stability issues appeared in a weak grid, that are specifically of concern to restoration, have to be considered as well. In order to improve the effectiveness of restoration planning, more advanced tools are desired to help operators to complete the task effectively when it happens.